Passing QFlags between threads



  • Dear all,

    using Qt4.8.7, I'm in trouble trying to connect a signal to a slot on a different thread when signal/slot argument contains a QFlags...

    first of all... is this possible at all ?

    I'm declaring my flags as usual, with

       Q_DECLARE_FLAGS (ACTRLFLAGS, ACTRLFLAG) 
    

    and

        Q_DECLARE_OPERATORS_FOR_FLAGS( NMyClass::ACTRLFLAGS )
    

    but this seems not enougth when the connection is (queued) between threads... then I've try registering the type with

       Q_DECLARE_METATYPE(NMyClass::ACTRLFLAGS)
    

    and

      qRegisterMetaType<NMyClass::ACTRLFLAGS>();
    

    but even if I don't see anymore an error regarding the connection at run-time, it simply doesn't work... my slot is not called at all...

    any ideas ?

    thanks in advance

    Giampaolo

    [Added code tags ~kshegunov]


  • Lifetime Qt Champion

    Hi,

    IIRC, you need to also provide the QDataStream operators for your flags and register them with qRegisterMetaTypeStreamOperators so they can be serialised in QVariant.



  • Hello SGaist...

    just for a test, I've replaced my QFlags with a plain int... and it doesn't work.... so the problem must be elsewhere...

    I'll try again tomorrow :D :D :D

    Best Regards
    
               Giampaolo

  • Moderators

    @iw2lsi Does it work in the same thread?



  • @iw2lsi Show us the code for the signal, slot, and where you connect one to the other.

    And if possible the code for the thread start and creation.


  • Qt Champions 2016

    @iw2lsi said in Passing QFlags between threads:

    qRegisterMetaType<NMyClass::ACTRLFLAGS>();
    

    but even if I don't see anymore an error regarding the connection at run-time, it simply doesn't work... my slot is not called at all...

    Depending on how you do the signal-slot connection and/or slot call you may need to adjust this line. Please show us the code for that as @ambershark mentioned.



  • Hi all,

    first of all, thanks for the support and sorry for the delay...

    The problem was in my receiver thread... basically my consumer process was blocking the event loop in a waitcondition, and that's why I was not receiving the signals... Nothing was wrong in the way my QFlags was registered on the meta-object system...

     thanks again,
    
              Giampaolo

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